feat: Umbrix branding - logo and name changes

- Changed app title from Hiddify to Umbrix in home page
- Added custom Umbrix logo (192x192 PNG)
- Updated intro page with Umbrix branding and gradient design
- Updated drawer menu with Umbrix logo
- Modified add profile modal with modern gradient cards
- Updated Russian translations (appTitle: Umbrix)

assets/translations/strings_ru.i18n.json

@@ -1,6 +1,6 @@
 {
   "general": {
-    "appTitle": "Hiddify",
+    "appTitle": "Umbrix",
     "reset": "Сброс",
     "toggle": {
       "enabled": "Включено",